The present invention relates generally to cathodic arc coating and, more particularly, to an improved target mounting system for cathodic arc cathodes.
The cathodic arc process is known in the art as a robust, relatively inexpensive technique for deposition of single and multi-component metallic and nonmetallic coatings. Cathodic arc deposition systems consist of a vacuum chamber which includes an anode, a power supply and a cathode. The cathode material is deposited during the operation of the system.
Often, these cathodes are typically mounted to the electrical source and means for cooling the cathode by means of a threaded stud. In some instances, cost and/or manufacturability considerations preclude making the entire cathode from the material of interest.
Thus, there remains a need for an improved cathodic arc coating apparatus able to mount less than a complete cathode target while, at the same time, providing sufficient strength to hold the cathode in place.
The present invention is directed to an apparatus for cathodic arc coating. The apparatus includes: a vacuum chamber which includes an anode; a power supply; and a cathode target assembly connected to the power supply. The cathode target assembly includes a cathode target and a target holder. In a preferred embodiment of the invention, an electrically conductive interlayer is located between the target and the target holder; and a cooling block in contact with the cathode target.
The cooling block includes a chamber adjacent to the cathode and a cooling fluid supply contained within the chamber. A fluid seal between the cooling block and the cathode prevents leakage of coolant into the vacuum chamber. The cooling fluid supply includes an inlet for providing cooling fluid into the chamber and an exit for withdrawing the fluid from the chamber.
The vacuum chamber includes an enclosed chamber and a staged pump for producing a vacuum therein. In the preferred embodiment, the power supply is a continuous DC power supply of greater than about 60 amps at about 20 volts.
In the preferred embodiment, the conductive interlayer is a layer of in situ solder such as a low melting point metal like indium. However, the conductive interlayer may be a sheet of metal foil formed from a ductile metal such as gold, silver or platinum.
Also, in the preferred embodiment, the target is puck-shaped and the target holder is cup-shaped for receiving the puck-shaped target. Pins may extend through the walls of the cup-shaped holder into the puck-shaped target to attach the target to the target holder.
In a second embodiment, the puck-shaped target further includes a shoulder portion, which extends beyond the base of the target and, wherein the shoulder of the target and the walls of the cup-shaped target holder are substantially co-extensive.
In a third embodiment, the shoulder of the puck-shaped target extends beyond the walls of the cup-shaped holder to form a mushroom shape.
Accordingly, one aspect of the present invention is to provide an apparatus for cathodic arc coating. The apparatus includes: a vacuum chamber which includes an anode; a power supply; and a cathode target assembly connected to the power supply, the assembly including: a cathode target and a target holder.
Another aspect of the present invention is to provide a mounted cathode assembly for a cathodic arc coating apparatus. The cathode target assembly includes: a target holder; a cathode target disposed within the target holder; and a conductive interlayer located between the target and the target holder.
Still another aspect of the present invention is to provide an apparatus for cathodic arc coating. The apparatus includes: a vacuum chamber which includes an anode; a power supply; a cathode target assembly connected to the power supply, the assembly including: a cathode target; a target holder; and a conductive interlayer located between the target and the target holder; and a cooling block in contact with the cathode target.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.